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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>Journal of Reliable Intelligent Environments 10 (2024) 299-318. URL:
https://doi.org/10.1007/s40860</journal-title>
      </journal-title-group>
      <issn pub-type="ppub">1613-0073</issn>
    </journal-meta>
    <article-meta>
      <article-id pub-id-type="doi">10.1145/3513092</article-id>
      <title-group>
        <article-title>mendation on Large-scale Datasets via Knowledge Prompting of Venues and Users</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Yuuki Tachioka</string-name>
          <email>tachioka.yuki@core.d-itlab.co.jp</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Workshop</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="editor">
          <string-name>Privacy-aware Recommendation, Location-based Services</string-name>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Denso IT Laboratory</institution>
          ,
          <addr-line>13F Shintora Yasuda Bldg., 4-3-1 Shimbashi, Minato-ku, Tokyo</addr-line>
          ,
          <country country="JP">Japan</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Point of Interest Recommendation, Large Language Model</institution>
          ,
          <addr-line>Knowledge Prompting, Sequential Recommendation</addr-line>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2023</year>
      </pub-date>
      <volume>6</volume>
      <fpage>299</fpage>
      <lpage>318</lpage>
      <abstract>
        <p>Accurate prediction of the next point of interest (POI) that a user will visit is important to location-based services for personalized and context-aware recommendation. Traditional approaches, particularly those based on collaborative filtering, struggle to fully utilize the semantic, temporal, and spatial information embedded in user behavior data. Although the emergence of large language models (LLMs) can capture semantic information, large-scale LLMs are infeasible for large-scale data due to computational constraints, as our experiment shows. In this paper, we propose an eficient and lightweight POI recommendation framework, KP4POI, that leverages small-scale LLM enhanced with knowledge prompting, which encodes knowledge graphs of venue and user into natural language. By transforming user and venue knowledge graphs into natural language prompts, our method enables LLMs to incorporate semantic, geographic, and social information efectively. Experiments on real-world datasets demonstrate that our approach improves recommendation quality while maintaining scalability.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        The proliferation of location-based services has precipitated an increasing demand for systems capable of
recommending the next Point of Interest (POI) that is relevant and useful to the user, conditioned on their
spatio-temporal check-in history. Such predictive capabilities are pivotal not only for improving
usercentric experiences, but also for optimizing marketing strategies through context-aware personalization
[
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. Traditional POI recommendation methods are mainly based on collaborative filtering (CF), which
models user-POI interactions using unique identifiers [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. Although efective to some extent in small
computational load, these methods are limited in modeling semantic similarity among POIs and fail to
consider sequential and spatial dependencies in check-in behaviors.
      </p>
      <p>
        Subsequently, many hybrid methods have been proposed that incorporate categorical, temporal, or
contextual information [
        <xref ref-type="bibr" rid="ref3 ref4 ref5 ref6">3, 4, 5, 6</xref>
        ]. Among them, recent deep learning approaches have employed graph
neural networks to encode high-order dependencies in heterogeneous spatial graphs [7, 8], and hybrid
models that combine matrix factorization with deep interactions have shown promise in mitigating data
sparsity and semantic heterogeneity [9, 10, 11]. Furthermore, sequential recommendation techniques
have been adapted to POI scenarios, using temporally localized user trajectories to model higher-order
transitions and intent-aware behavior [12, 13].
      </p>
      <p>With the rise of large language models (LLMs), new avenues for context-aware recommendation
have emerged [14, 15, 16]. Two main types of LLM-based POI recommendation methods have gained
attention: prompt-based methods and embedding-based methods, as shown in Figs. 1 (a) and (b).
Prompt-based methods convert recommendation tasks into natural language format and use compact
LLMs to generate candidates [17]. These methods are computationally eficient but often lack the ability
to integrate structured knowledge such as venue categories or spatial relationships. Embedding-based
methods generate semantic user embeddings from user check-in history and POI embeddings from
POI attributes by using large-scale LLMs [18, 19, 20, 21], and calculate the similarity between them at
Workshop on Recommenders in Tourism (RecTour 2025), September 22, 2025, co-located with the 19th ACM Conference on</p>
      <p>CEUR</p>
      <p>ceur-ws.org
the cost of heavy fine-tuning and inference. Although expressive, these methods are computationally
demanding and impractical for large-scale datasets [21, 22].</p>
      <p>To address this challenge, we designed a framework, KP4POI, that enriches prompt-based methods
with structured knowledge through knowledge prompting (KP) [23, 24], as shown in Fig. 1 (c). Specifically,
we transform venue and user knowledge graphs (KGs) into natural language prompts, allowing compact
LLMs to efectively utilize not only venue attributes (e.g., category, location) but also user context (e.g.,
social connections) during prediction. In contrast to embedding-based approaches, our method achieves
eficiency by leveraging compact LLMs, while the integration of KGs can help mitigate hallucinations in
LLM predictions and improve accuracy [25]. Moreover, because our method uses structured knowledge,
such as venue categories, addresses, or user communities, to substitute for raw location coordinates, it
partially supports privacy-aware settings where fine-grained location data may not be available [ 26]. In
such scenarios, user-level knowledge, such as social groupings, can further complement missing venue
information, enabling robust recommendations even under limited or anonymized metadata.</p>
      <p>In this paper, we compare our KP4POI with embedding-based methods in terms of fine-tuning
eficiency on large-scale POI datasets. We examine the contribution of diferent types of
knowledge—specifically, categorical afinity and geographic proximity—and assess the utility of user KP derived from
social graphs [27]. Our findings demonstrate that compact LLMs augmented with structured knowledge
ofer a practical and scalable solution for personalized POI recommendation.</p>
    </sec>
    <sec id="sec-2">
      <title>2. LLM-empowered POI recommendation</title>
      <p>As discussed in Section 1, LLM-empowered POI recommendation methods can be categorized into
prompt-based and embedding-based approaches. One of the most important prompt-based methods
is P5. The P5 uses a prompt to reformulate the recommendation task as a natural language task by
encoding the IDs of the recommendation items [17] with the masked personalized prompt (MPP)
[17, 23]. Fig. 2 shows an example of MPP templates, where  denotes a set of prompt templates to
encode historical check-ins as natural language. The MPP   (,    ;  ) is constructed for the user 
based on the IDs of previously visited  venues    = { 1, … ,   }. The next POI target is masked using
multiple templates  , where the wider variety of templates is important [28]. Based on this prompt,
an LLM can predict the next POI ID, denoted  +1 , that the user may be interested in. Combining the
venue knowledge prompt with the standard MPP in the following final input:
  (,    ) = [ ]

(,    ;  )[ ].</p>
      <p>(1)
In Eq. (1), the special token [SP] serves as a delimiter separating the user’s check-in history from the
appended knowledge prompts. To minimize vocabulary size and improve generalization, eficient
tokenization represents IDs split into two-digit segments, e.g., 1298 as &lt;12&gt;&lt;98&gt;. Since the output
in P5 is ID, high generative capacity is not required and performance and speed are balanced using
a compact LLM such as T5 [29]. Advanced recommendation methods such as Prompt Distillation for
Eficient LLM-based Recommendation (POD) [ 28] and KP [23] are based on P5. POD distills discrete
using diferent types of templates  .
prompt templates into task-specific continuous prompt vectors, thus improving the training eficiency
of LLM-based recommendation systems. Functionally, POD and P5 difer only in that POD uses multiple
prompt templates [28].</p>
      <p>Instead of prompting, embedding-based methods directly use LLM embeddings to make
recommendations [21]. However, embedding-based methods that use large-scale LLMs demand a high computational
load because the entire check-in history must be inputted to LLM for inference as a natural language
prompt. Both fine-tuning and inference require high computational load. Section 4.2.1 compares the
ifne-tuning time of two types of methods.</p>
    </sec>
    <sec id="sec-3">
      <title>3. KP4POI: prompt-based POI recommendation with knowledge prompting</title>
      <p>Building on the motivation outlined in Section 1, we present KP4POI, a prompt-based POI
recommendation framework enhanced by structured KP. KP4POI leverages knowledge about the venue and user
in a natural language format to guide LLMs for efective recommendation. This section details the
architecture of KP4POI and describes how KPs are generated and integrated into the LLM pipeline.</p>
      <sec id="sec-3-1">
        <title>3.1. Venue knowledge prompting</title>
        <p>The knowledge about the venues can be represented as KGs. Public datasets used in the experiment may
provide venue information, such as category or latitude / longitude (lat/lon), which can be converted to
addresses. For POI recommendation, categorical afinity and geographical proximity play an important
role [30]. Categorical afinity [ 31, 32] refers to co-occurrence of categories (e.g., visiting a train station
before an ofice), while geographical proximity [ 33, 34] involves nearby locations (e.g., dining at a
restaurant close to the ofice). This knowledge can be concatenated into MPPs in the form of a KP.
To measure geometrical proximity, to address privacy concerns, reverse-geocoded address features
are aggregated at the street level (NYC) or chome (block) (Tokyo), ensuring that no fine-grained and
personally identifiable location information is used. At inference time, these features are retrieved from
venue metadata and do not require real-time or private user data.</p>
        <p>KGs consist of triples (head / relation / tail) represented as (ℎ,  , ) . To incorporate KG
knowledge into LLM, a KP transforms a KG triple using a relation-specific template   , as illustrated in
Fig. 3. A KG  = ( , category,   ) is converted using the relation-related template   () =
“The category of  is   ” when  = category. Let   be the set of KGs related to the venue  . A
venue KP   can be generated from the KGs of the venues visited    as follows:   (   ,   ) =
⋃∈   ⋃∈    (), where ⋃ denotes the concatenation of prompts. The final prompt combining venue</p>
        <p>For example, for a user who visited  1 ( 1 = ( 1, category, ) ) then  2 ( 2 = ( 2, category, ) )), the final
prompt becomes: “[ ]

[ ]</p>
        <p>The category of  1 is  . The category of  2 is  . [ ] ”.</p>
      </sec>
      <sec id="sec-3-2">
        <title>3.2. User knowledge prompting</title>
        <p>User-specific information has been shown to improve the performance of recommendation [ 27].
Attributes such as gender and age can ofer valuable personalization signals. However, such personal data
are rarely available in POI recommendation due to heightened privacy concerns, especially because
high-resolution location data can inadvertently expose sensitive details such as a user’s residence or
workplace. In contrast, location-based social networks like Foursquare often include user social graphs,
which are less sensitive and are more readily available. These social graphs can implicitly capture
behavioral traits and allow for unsupervised grouping of users with similar characteristics. When a
social graph is available, user clustering can be efective for POI recommendation [ 35].</p>
        <p>To take advantage of this, we apply graph partitioning methods [36] to identify user communities in
the social graph. Each user is assigned a community that represents interpretable group-level
characteristics. Given that the POI recommendation benefits from approaches using graph neural networks
[7, 8] or matrix factorization [9, 10, 11], we derive community labels using node embeddings [37] using
node2vec, and cluster them [38] by k-means++ clustering [39]. Each cluster ID serves as a
communitylevel pseudo-attribute label that represents the user’s social context, where each user is assigned to
exactly one cluster. These community labels can be encoded as KG triples (, community, )
. We
can convert them into natural language prompts using a relation-specific template as in Fig. 4, and
incorporate them into the model via user KP. This allows the compact LLM to benefit from social
information even in privacy-aware settings where fine-grained personal metadata are not accessible 1.
and the final prompt combining user knowledge is given by:</p>
        <p>Let   be the set of KG triples related to user  . Then, a user KP   is  
(,   ) = ⋃∈ 
  ()
(2)
(3)
(4)
In KP4POI, the loss function maximizes the likelihood of the next POI  +1 in the model  as
  (, 
  ,   ,   ) =   (, 
  ,   ) 
(,</p>
        <p>)[ ].</p>
        <p>=1
ℒ = − ∑
∑ log   ( +1 |  (, 
  ,   ,   )).</p>
        <sec id="sec-3-2-1">
          <title>For inference, the beam search is used to predict the next POI list.</title>
        </sec>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>4. Experiments</title>
      <sec id="sec-4-1">
        <title>4.1. Experimental setup</title>
        <p>For POI recommendation tasks, LLM-based methods have generally been efective [ 21]. Among those
utilizing large-scale LLM such as Llama, SeCor and soft prompting [ 40] demonstrated the highest
performance. Both SeCor and our method are fine-tuned from a pre-trained Llama2-7B and T5-small,
respectively. SeCor requires an additional step of CF training. However, as shown in Table 2, the use of
1Note that our approach derives community labels by clustering user embeddings obtained from the social graph. Therefore,
user KP is applicable only to datasets that include explicit social relations (WWW2019 and Gowalla). For datasets without
social graphs (NYC and TKY), user KP cannot be constructed.
large-scale LLMs is impractical for large-scale datasets2. Except for methods using large-scale LLMs,
the POD and collaborative filter-based seq2graph [ 41] performed comparable.</p>
        <p>We compare our method 3 with P54 and SeCor, as they represent two contrasting baselines: P5
as a prompt-based approach and SeCor as an embedding-based approach using large-scale LLM. We
primarily compare with P5 because it represents a compact, prompt-based LLM recommender that is
closest in spirit to our framework. While traditional baselines such as popularity or matrix factorization
would also be informative, we leave their integration for future work since our focus here is to evaluate
the eficiency and efectiveness of knowledge prompting relative to existing LLM-based approaches.</p>
        <p>We used T5-small (60.5M parameters) as the backbone, which is much smaller than Llama-7B. The
model used 512 dimensions and eight multihead attention. AdamW was used with a maximum learning
rate of 0.001, batch size 64, and 100 epochs. The best model was selected on the basis of the validation
performance. Following previous work [21, 42], the check-ins were sorted chronologically by user.
Users with fewer than 10 check-ins and venues visited only once or twice were removed. Three types
of venue KG were used: address, lat/lon5, and category such as restaurant. KP was implemented based
on KP4SR6. The evaluation used NDCG@ and Recall@ for  = {5, 10, 50} in a leave-one-out setting7.
The last two venues were reserved for testing and predicted by models fine-tuned on the remaining
data. We used a paired t-test with Bonferroni correction to assess the significance between P5 and our
KP4POI.</p>
        <p>Table 1 shows the statistics of four Foursquare datasets8 (NYC, TKY, TIST2015, and WWW2019) and
one Gowalla dataset9, where Foursquare and Gowalla are location-based social networks with user
check-ins. NYC and TKY are small, commonly used, and suitable for parametric studies. TIST2015 and
WWW2019 are used to test scalability, because they are large-scale. Among the four datasets, only
WWW2019 and Gowalla contain explicit social graphs. Since our method requires social graphs to
derive community labels via clustering, user KP is only available for these two datasets</p>
        <p>The NYC and TKY dataset [43] contains check-ins in New York City (NYC) and Tokyo (TKY), where
2Although we used the oficial implementation ( https://github.com/siri-ya/SeCor), we could not reproduce the results reported
in [21].
3https://github.com/DensoITLab/KP4POI
4P5 and POD are functionally equivalent, except that POD uses multiple prompt templates [28], while P5 in our implementation
employs 11 templates to ensure comparability.
5In [21], lat/lon was converted to address. We validated the efectiveness of this.
6https://github.com/zhaijianyang/KP4SR
7We focus on accuracy metrics (NDCG, Recall) as in prior work, leaving diversity/coverage for future work.
8https://sites.google.com/site/yangdingqi/home/foursquare-dataset
9https://snap.stanford.edu/data/loc-gowalla.html</p>
        <p>Recall</p>
        <p>NDCG</p>
        <p>Recall
Method
P5(POD) 0.2383 0.2437 0.3084 0.3250 0.2135 0.2243 0.2861 0.3188
KP4POI(add) 0.2395 0.2431 0.3121 0.3232 0.2162 0.2287† 0.2904† 0.3280**
KP4POI(lat/lon) 0.2385 0.2436 0.3102 0.3259 0.2175 0.2287† 0.2883† 0.3227*
KP4POI(add+lat/lon) 0.2399 0.2451 0.3121 0.3278 0.2144 0.2256 0.2887 0.3227
KP4POI(cat) 0.2457* 0.2516* 0.3075 0.3250 0.2197* 0.2307* 0.2909** 0.3245**
KP4POI(cat+add) 0.2521** 0.2562** 0.3112** 0.3232 0.2196* 0.2291† 0.2918* 0.3210†
KP4POI(cat+add+lat/lon) 0.2508** 0.2560** 0.3130** 0.3287** 0.2197* 0.2290† 0.2913** 0.3201
each check-in includes a timestamp, lat/lon, and category. The addresses were obtained by reverse
geocoding: NYC via Nominatim10 (“street” level), TKY via Yahoo!11 (“chome” level). To avoid invading
privacy and reduce the number of reverse geocoding, the coordinates were rounded to three decimal
places. The TIST 2015 dataset [44] includes check-ins from 415 cities in 77 countries, where each city
had at least 10K check-ins, and the city names were used as addresses. The WWW 2019 dataset [45]
covers global check-ins12 and includes check-ins and user social graphs13. The Gowalla dataset [46]
covers global check-ins14 and includes a social graph, where because many users had few check-ins, we
retained only those with 10+ check-ins (69,705 of 196,591).</p>
      </sec>
      <sec id="sec-4-2">
        <title>4.2. Results and Discussions</title>
        <p>We designed four types of research questions: one concerning fine-tuning time and the applicability of
LLM (4.2.1), two that address venue KP (4.2.2 and 4.2.3), and one exploring user KP (4.2.4).
4.2.1. RQ1: Can large-scale LLMs be applied to large-scale POI recommendation?
Table 2 shows the fine-tuning time required by our KP4POI using T5-small and SeCor using Llama2-7B.
The gap between the two is significant. In fact, even in the experiments of [ 21], only 850,010 check-ins
out of 5 million were used from the Gowalla dataset. Although parallelization makes it feasible to run
experiments on datasets of the NYC/TKY scale, applying large-scale LLMs solely to obtain embeddings
for large-scale data is impractical. Therefore, it is essential to improve performance by using compact
10https://nominatim.org/
11https://developer.yahoo.co.jp/webapi/map/openlocalplatform/v1/reversegeocoder.html
12This does not include city names but does include lat/lon and country codes. We used 629 major cities (TIST2015 cities +
capital cities) and matched check-ins to the closest city with the same country code.
13Although two types of social graph are provided, we used the newer one.
14Because country codes are not provided, we matched each check-in to the nearest city using lat/lon.
LLMs. In addition to the significant diference in the fine-tuning time (Table
implications emerge.</p>
        <sec id="sec-4-2-1">
          <title>2), several practical</title>
          <p>• Scalability: Our method handles tens of millions of check-ins with fine-tuning times under 10
minutes per epoch, making it practical for real-time model updates in production.
• Cost-eficiency : Unlike large-scale LLMs, which require substantial GPU memory and power,
T5-small requires only modest computational resources, making it accessible to institutions with
limited hardware.
• Maintainability: The lightweight architecture allows for rapid fine-tuning as user behavior
evolves, facilitating continuous learning without downtime or extensive costs.
• Broader applicability: The method is suitable not only for centralized cloud systems, but also
for edge deployment scenarios, promoting POI personalization in privacy-sensitive or ofline-first
environments.</p>
          <p>These findings reafirm that KP4POI that enhances small LLMs with structured knowledge is a practical
and scalable direction for future POI recommendation systems.
4.2.2. RQ2: Which is more efective: address or latitude and longitude?
We compare KP4POI(add) and KP4POI(lat/lon) to assess the contribution of diferent types of
geographical knowledge15. Although Table 3 shows only small diferences between address and lat/lon in the NYC
dataset due to the limited granularity of US street-level addresses, significant gains in TKY highlight the
usefulness of the hierarchical structure of Japanese addresses (e.g., prefecture → city → chome (block)),
which encodes spatial clustering and provides richer cues than raw coordinates. This also explains
why the overall contribution of address-based knowledge may appear small in some datasets: when
addresses lack hierarchical depth or are too coarse, they fail to capture the fine-grained distances that
strongly influence tourist behaviour. In practice, however, address-based knowledge remains easier
to interpret, more stable against noise, and often more accessible in privacy-sensitive or anonymized
datasets where lat/lon is not disclosed. In contrast, latitude/longitude directly preserves precise spatial
proximity. Thus, while their relative performance diferences are modest, the two variants capture
complementary aspects of geographical information, and address-level knowledge can sometimes
substitute for exact coordinates in real-world applications.
4.2.3. RQ3: Which is more efective: geographical information or category?
Table 3 also includes performance metrics when KP4POI(cat) is applied to the NYC and TKY datasets.
Address information contributes mainly to improvements in Recall, while category information mainly
enhances NDCG, which shows that geographical information and category can have diferent types
of useful information. The last two rows of Table 3 show the results when combining the address or
lat/lon with the category. In the NYC dataset, this combination significantly improved performance in
all metrics (with 1% significance), demonstrating the efectiveness of using both types of knowledge.
KP4POI(cat+add+lat/lon) improved NDCG@5 by 1.3% compared to P5(POD) in NYC.</p>
          <p>Table 4 presents the results of similar experiments conducted on a large-scale dataset. A consistent
trend is also observed here: The combination of both leads to the best results from both perspectives.
These results suggest that category-based knowledge tends to improve ranking precision (NDCG),
while geographical knowledge often improves recall. Although not absolute, this complementary
efect was observed consistently across datasets. Importantly, combining both sources of knowledge
results in statistically significant improvements in all metrics (Table 3, Table 4). This demonstrates
the complementary nature of the two: while semantic similarity guides “what” the user wants, the
spatial context informs “where” it is realistically accessible. This robustness is particularly beneficial in
large-scale settings like TIST2015 and WWW2019, where venue diversity and user heterogeneity are
15KP4POI without add is functionally equivalent to P5, as it only uses sequential prompts without additional knowledge. For
this reason, we do not report it separately.</p>
          <p>NDCG</p>
          <p>TIST2015
0.1863
0.1928**
0.1937**
0.2003**
0.2386
0.2413**
0.2394**
0.2440**</p>
          <p>Recall
0.2533
0.2753**
0.2565**
0.2775**</p>
          <p>WWW2019
NDCG
0.1905
0.1915**
0.1970**
0.1988**
0.1927
0.1988**
0.1999**
0.2058**
0.2480
0.2508**
0.2481**
0.2529**
0.2548
0.2730**
0.2570**
0.2743**</p>
          <p>NDCG</p>
          <p>WWW2019
0.1927
0.1946**
0.1988**
0.1993**
0.2061**
0.2480
0.2490**
0.2508**
0.2513**
0.2526**</p>
          <p>Recall
0.2548
0.2612**
0.2730**
0.2732**
0.2741**</p>
          <p>Gowalla
NDCG</p>
          <p>Recall
0.1929
0.1930
0.1924
0.1927
0.1950
0.1956†
0.1979**
0.1983**
pronounced. For that case, enriching language models with multifaceted knowledge, both semantic and
geographic, yields more reliable and context-aware POI recommendations.
4.2.4. RQ4: Does user information improve performance?
Table 5 shows the performance results when the user KP (KP4POI(u)) is applied to the WWW2019
dataset. Except for NDCG@5, all metrics show statistically significant improvements at the 1% level.
This indicates that even when only facility IDs are available without lat/lon due to privacy issues, user
KP significantly improves performance. When used together with category or address information, the
added benefit of user KP is minimal, suggesting that social grouping can be learned implicitly through
check-in records.</p>
          <p>Table 5 also shows the corresponding results in the Gowalla dataset. However, incorporating
address information leads to statistically significant improvements in NDCG@10 and Rec@10 (1% level).
Similarly, the user KP significantly improves NDCG@10 and Rec@10, confirming its efectiveness. The
combination of address and user information does not provide an additional benefit.</p>
          <p>These results demonstrate the efectiveness of KP4POI(u), particularly in environments where venue
metadata are limited or unavailable. Community-level embeddings serve as surrogates for missing
contextual cues, enabling the model to generalize based on social afinity and collective behavior
patterns. Although user KP significantly improves performance when used alone, its marginal benefit
in combination with venue information suggests some redundancy between social and spatial signals.
For privacy-sensitive contexts, user KP can be efective when explicit social graphs are available (e.g.,
in Gowalla or WWW2019). However, its utility for cold-start users in real-world scenarios without
such graphs may be limited. Its eficiency and interpretability further support its inclusion in scalable
POI recommendation pipelines.</p>
          <p>Although the contribution of user-knowledge prompts appears small, this can be partly explained
by the characteristics of the datasets. Only a fraction of users are connected on social graphs, and
clustering from sparse interactions yields coarse community labels. Consequently, the additional signal
provided by user KP is weaker than the venue-based knowledge. However, user-level information
remains valuable in privacy-sensitive contexts or datasets where precise location data are unavailable,
as it can still capture group-level behavioral tendencies.</p>
        </sec>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>5. Conclusion</title>
      <p>In this paper, we proposed KP4POI, a knowledge-enhanced POI recommendation framework that uses
compact LLMs with knowledge prompting derived from venues and users. By reformulating POI
recommendation as a natural language task, our method integrates semantic and contextual knowledge
without incurring the heavy computational costs of large-scale embedding-based approaches. Extensive
experiments on four real-world datasets demonstrated that KP4POI achieves competitive performance
while reducing training time and resource requirements. In addition, our ablation study showed
that category- and geography-based knowledge prompts contribute diferently to recommendation
performance, and their complementary efects improve both ranking precision and recall. Although we
leave for future work a more comprehensive evaluation, including additional baselines (e.g., popularity,
matrix factorization), user cold-start scenarios, and broader recommendation metrics such as diversity
and catalog coverage, these results highlight the practicality of incorporating structured knowledge
into lightweight LLMs for POI recommendation.</p>
      <p>Our findings indicate that KP4POI ofers a scalable, interpretable, and privacy-aware solution to POI
recommendation. This work opens promising directions for building more intelligent, adaptive, and
eficient location-based services using LLMs augmented by external knowledge.</p>
    </sec>
    <sec id="sec-6">
      <title>Declaration on Generative AI</title>
      <p>During the preparation of this work, the author used ChatGPT-4 and writefull in order to: Grammar
and spelling check. After using these services, the author reviewed and edited the content as needed
and takes full responsibility for the publication’s content.
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