## 1 Introduction  
Given the ever-increasing importance of the World Wide Web as a source of information, adequate Web archiving and preservation has become a cultural necessity for preserving knowledge. The report _Sustainable Economics for a Digital Planet_[1] states that \"the first challenge for preservation arises when demand is diffuse or weakly articulated.\" This is especially the case for non-traditional digital publications, e.g., blogs, collaborative space or digital lab books. The challenge with new forms of publications is that there can be a lack of alignment between what institutions see as worth preserving, what the owners see as of current value and the incentive to preserve together with the rapidness at which decisions have to be made. For ephemeral publications, such as the Web, this misalignment often results in irreparable loss. Given the deluge of digital information created and this situation of uncertainty, the first necessary step is to be able to respond quickly, even if in a preliminary fashion, by the timely creation of archives, with minimum overhead, enabling more costly preservation actions further down the line. This is the challenge that the ARCOMEM [2] project is addressing. In addition to the \"common\" challenges of digital preservation, such as media decay, technological obsolescence, authenticity and integrity issues, Web preservation has to deal with the sheer size and ever-increasing growth and change rate of Web data. [PERSON] _et al._[3] showed that the Web is growing by more than 8% per week and that after one year, 40% of the pages are still accessible, while 60% of the pages are new or changed. This is to be contrasted with the fact that, according to [PERSON] _et al._[4], only approximately 40 Web archiving initiatives are active, which involve only about 270 people worldwide. Hence, the selection of content sources becomes a crucial and challenging task for archival organizations. A pivotal factor for enabling next-generation Web archives is crawling. Crawlers are complex programs that nevertheless implement a simple process: follow links and retrieve Web pages. In the ARCOMEM approach, however, crawling is much more complex, as it is enriched with functionality dealing with novel requirements. Instead of following a \"collect-all\" strategy, archival organizations are trying to build community memories that reflect the diversity of information in which people are interested. Community memories largely revolve around events and the entities related to them, such as persons, organizations and locations. These may be unique events, such as the first landing on the moon or a natural disaster, or regularly occurring events, such as elections or TV serials. Thus, entities and events are natural candidates for focusing new types of content acquisition processes in preservation, as well as for archive enrichment. Current Web crawler technology is mainly inspired or based on crawlers for search engines. Therefore, they have limited or no notion of topics, entities, events or the Social Web context. In this article, we want to present the architecture of a new kind of Web crawler that addresses the special needs of Web archiving organizations. This new crawler generation will analyze and mine the rich social tapestry of the Social Web to find clues for deciding what should be preserved (based on its reflection in the Social Web), to contextualize content within digital archives based on their Social Web context and to determine how to best preserve this context. Contextualization based on the Social Web will be complemented by exploring topic-centered, event-centered and entity-centered processes for content appraisal and acquisition, as well as for rich preservation. In this paper, we give an overview of the crawler architecture implemented within the ARCOMEM project that addresses the requirements mentioned above. The paper goes beyond our initial work in [5] by providing more details about the different phases, the data management and analysis modules.